This invention relates to the navigation of medical devices in magnetic fields, and in particular to the navigation of medical devices in magnetic resonance imaging equipment.
The navigation of a medical device in an operating region with the aid of an externally applied magnetic field, such as that provided by an MRI device, by using a controllable variable magnetic moment in the device tip has been proposed, and is in fact the subject of Kuhn, U.S. Pat. No. 6,216,026, Arenson, U.S. Pat. No. 6,304,769, and Hastings et al., U.S. Pat. No. 6,401,723. One way of creating a controllable variable magnetic moment in a medical device disclosed in these patents is through controlled variable currents in tiny coils in the distal end of the device, and preferably a set of at least three mutually perpendicular coils. However, it can be expensive to fabricate such coils and assemble them into the medical device. Furthermore, the magnetic field can cause significant heating of the long electrical leads to the coils.